1. Field of the Invention
The present invention relates to an image-capturing apparatus and method for capturing an image by using a solid-state image-capturing device, to an expression evaluation apparatus for evaluating the expression of an image-captured face, and to a program for performing the processing thereof.
2. Description of the Related Art
In image-capturing apparatuses, a so-called self-timer function of automatically releasing a shutter button after a fixed period of time has elapsed from when an operation for depressing the shutter is performed is typically installed in not only silver-halide cameras, but also digital still cameras. However, the timing at which a shutter is released by the self-timer function is determined in advance. Therefore, it is difficult to guarantee that a person being image-captured has a desired expression on their face at the time the shutter is released, and there is a problem in that unsatisfactory photographs may be often taken.
On the other hand, in recent years, image processing technologies for performing digital computation processing on the basis of an image signal have progressed rapidly, and as an example thereof, a technology for detecting the face of a human being from an image is known. There is a known face detection technology in which, for example, a difference in luminance between two pixels in a face image is learnt as an amount of a feature, an estimated value indicating whether or not a predetermined region in an input image is to be computed on the basis of the feature amount, and whether or not the image in the region is a face is finally determined on the basis of the estimated value of one or more estimated values (refer to, for example, Japanese Unexamined Patent Application Publication No. 2005-157679 (Paragraph Nos. [0040] to [0052], FIG. 1).
The development of such face detection technologies has progressed to a level at which such a technology can be installed into a digital image-capturing apparatus for performing image capturing using a solid-state image-capturing device, such as a digital still camera. Recently, furthermore, a technology for determining the expression of a detected face has attracted attention. It has been considered that, for example, the expression of a face of an image-captured person could be evaluated for each captured image from the image signal in which a plurality of frames are continuously captured, so that an appropriate image can be selected on the basis of the information on those evaluations (refer to, for example, Japanese Unexamined Patent Application Publication No. 2004-46591 (Paragraph Nos. [0063] to [0071], FIG. 3).